One of the most challenging but important aspects for government agencies charged with handling emergency service calls (e.g. 911 calls) is quickly and accurately determining the appropriate location to dispatch the needed emergency resources. The individuals making such calls are often under high levels of stress and may not be able to provide emergency service operators with accurate location information.
Enhanced 911 (“E911”) and Next Generation 911 (“NG-911”) are standards defined by the National Emergency Number Association (NENA) used in the United States and Canada for linking emergency callers with the appropriate public resources. Originating call location determination is an important concept in the way that the emergency service systems work, specifically being able to immediately and accurately determine the location corresponding to the origination of the phone call. The type of originating device affects the manner in which the originating call location may be determined. For instance, landline (or wireline) calls are handled differently than calls from cellular phones or voice-over-IP (VoIP) telephones. Unlike cellular or VoIP phones, whose physical location at any given time may be independent of any fixed address associated with the assigned telephone number, wireline calls can generally be associated with a single fixed location, such as the customer's billing address. However, a wireline phone is not aware of its own physical location. After 9-1-1 is dialed, while the caller's voice is being delivered to an appropriate emergency services operator, background processes are automatically determining the call's originating location. Ideally, the location information is delivered to the emergency services operator simultaneously with the voice call.
In a legacy E911 system when a wireline telephone dials a telephone number, a connection is opened over a local section of a public switch telephone network (PSTN) to a local telephone exchange. In addition to a voice communication channel, the outgoing call also transmits the originating telephone number, our automatic number information (ANI). For non-emergency calls, the exchange determines how to route the call across the PSTN to the line associated with the dialed number so that a voice communication connection can be made between the originating wireline telephone and the destination line. However, if the number dialed is an emergency services number, special handling is required because there is no single telephone line or destination associated with the number. Instead, the originating wireline telephone should be connected to the Public Safety Answering Points (PSAPs) that serves the region the emergency call is originating from. (Depending on the geography of the region, there may be multiple PSAPs associated the same exchange and one PSAP may cover multiple exchanges.) Each PSAP covers a particular emergency service zone, which is determined by the dispatch and response arrangements for the fire, police, and medical services for a particular area. Thus, when the exchange recognizes an emergency services call, it switches the call to a selective router, which uses the originating call's ANI to determine the appropriate PSAP to connect with the call.
The PSAP receives the call, including the voice channel and ANI and must then determine the caller's location. The PSAP queries an Automatic Location Information (ALI) database with the originating call's ANI. The ALI database, which is often maintained on behalf of local governments by contracted private third parties, such as the local telephone service provider (TSP). The ALI database uses the telephone number assigned to the originating wireline telephone as a search key. The ALI record associated with the query, referred to as caller location information (CLI) is then returned to the PSAP where it is associated to the specific operator receiving the call and the address information is displayed on the operator's computer screen.
The Caller Location Information (CLI) provided is normally integrated into the PSAP's computer-assisted dispatch system. Early systems provided text display of the caller's address, call history and available emergency response resources. More modern computer-aided dispatch systems utilize geographic information systems (GIS) to implement real-time on-screen E911 street map displays to highlight information such as the caller's position, nearest available emergency responders and other relevant information such as fire hydrants, hazardous materials and/or other data maintained by the city.
Conventionally, ALI database is maintained in a traditional database management system (DBMS), which consists of rows of information utilizing a primary retrieval key of the origination phone number. In this scenario, when the originating phone number is submitted by the PSAP's call handling equipment to the location information provider, looked up in the DBMS-based ALI database, and the applicable location information then returned to the PSAP for use in handling and acting upon the call.